1. Field
The present invention relates to a device protecting a power factor correction (PFC) in three-phase power supply (hereinafter referred to as a three-phase PFC protection device) and a method of controlling the same, and more particularly to a device for protecting and controlling a PFC caused by an abnormal or erroneous current of a three-phase inverter.
2. Description of the Related Art
Generally, an inverter is a power-supply converter (also called a power converter) converting a DC voltage into a three-phase AC voltage (U, V, W). Due to high energy efficiency and convenience of output control, the inverter has been generally used to control motors for use in a variety of electronic products (e.g., washing machines, refrigerators, air-conditioners, microwave ovens, and elevators).
A rectifying circuit rectifying a commercial AC power into a DC voltage and smoothing this rectified DC voltage is connected to the above-mentioned inverter, such that the DC voltage smoothened to a predetermined level is provided to the inverter. A power factor of this rectifying circuit is very low, i.e., about 0.5-0.6. Due to a phase difference between an input voltage (i.e., a voltage of AC power) and an input current (i.e., a current of AC power), a power factor is decreased, such that there arises a loss of power consumption caused by a reactive power.
In order to solve the above-mentioned problems, a conventional art carries out power factor correction (PFC) operations, which corrects a power factor to prevent the occurrence of a phase difference between an input voltage and an input current, using a switching control scheme. This switching control scheme detects a zero-crossing point of an input voltage, turns on a switching element at the detected point, turns off the switching element after the lapse of a predetermined period of time, and maintains an OFF status of the switching element until reaching a zero-crossing point of the next input voltage.
Specifically, if the switching control scheme for the power factor correction (PFC) is applied to a three-phase inverter which uses a three-phase power supply (i.e., R-, S-, and T-phases) to power on electronic products of large amounts of power consumption, and a mis-connection (or non-connection) occurs in a power-supply input terminal applied to a reactor and a switching element due to a mistake of a manufacturer, a current applied to the switching element becomes an abnormal current (e.g., a low current or overcurrent), such that it is impossible to carry out the PFC control. As a result, the problems of a harmonic wave and a power factor occur, and an overheated circuit also occurs. Although the PFC is not controlled due to a poor reactor condition or a mis-connection, this error condition is not displayed, such that the conventional system may be unavoidably operated under an unstable status.